The PAS, developed by us for the purposes of this study, is a performance-based measure of preschoolers’ ability to engage in a sustained cycle of scientific inquiry around physical science phenomena. In the present study, two PAS tasks were used to examine children’s science ability in relation to water related science phenomena: floating and sinking, and water level. Both tasks were designed to elicit data on children’s extended reasoning process through a sequence of related questions. In particular, children were asked to (a) make an initial or first prediction about an event (Prediction 1); (b) perform, observe, and describe the event (Observation); and (c) make a second prediction about an analogous event involving a new set of objects (Prediction 2). The scores for the three items in each task were averaged to create a composite score. (author abstract)